I slept any way I chose through all pg even with my twins. I always woke and turned cause I was uncomfortable and be the end of you pg that weight on your back pretty much wakes you straight away!

I did have an issue with it once. I was having an ultrasound for the twins which took over an hour and I was on my back the whole time. I felt very faint and had cold sweats. All they got me to do was turn on my side for a couple of minutes then straight back onto my back. So I guess if they weren't overly fussed about it I would say its not a huge issue.

And come to think of it they warn us of the dangers of listeria, smoking, drugs and drinking whilst pg. If it was something really dangerous I think they would be informing us?